The present invention relates to a positive-working photoresist composition or, more particularly, to a positive-working photoresist composition which is capable of giving a patterned resist layer exhibiting excellent adhesion to the substrate surface with a surface film of silicon oxide or silicon nitride without suffering the troubles of incomplete or disordered etching in the subsequent steps in the manufacture of various kinds of electronic devices such as semiconductor devices, TFTs (thin-film transistors), liquid-crystal display panels and the like and which is very stable in connection with the photosensitivity in the pattern-wise exposure to actinic rays and film-thickness retention in the development treatment in the lapse of long time for storage.
As is known, the photolithographic patterning work to form a patterned resist layer on the substrate surface is a well established technology in the manufacturing process of various kinds of electronic devices such as semiconductor devices, TFTs, liquid-crystal display panels and the like, in which the substrate surface is provided with a coating layer of a photoresist composition which is exposed pattern-wise to actinic rays through a patterned photomask to form a latent image of the pattern followed by a development treatment of the latent image to form a patterned resist layer which serves as a protective resist in the subsequent processing such as etching. It is sometimes the case that the surface of the substrate, such as a semiconductor silicon wafer, is provided with a surface film of silicon oxide or silicon nitride or the substrate per se is made from a metallic material such as aluminum, tantalum, molybdenum, chromium and the like.
Of the two types of the photoresist compositions including the positive-working and negative-working ones, the photoresist compositions of the former type are preferred to the latter type in most applications. Typically, a positive-working photoresist composition is formulated with an alkali-soluble resinous ingredient such as novolac resins as a film-forming agent and a quinonediazido group-containing compound or, in particular, a quinonediazido group-containing benzophenone compound as a photosensitizing agent (see, for example, U.S. Pat. No. 4,377,631 and Japanese Patent Kokai No. 62-35349, No. 1-142548 and No. 1-179147).
One of the important requirements in the photolithographic patterning work is firm adhesive bonding between the substrate surface and the patterned resist layer, especially, when the surface of the substrate, such as a semiconductor silicon wafer, is provided with a surface film of silicon oxide or silicon nitride or the substrate per se is made from a metallic material such as aluminum, tantalum, molybdenum, chromium and the like in the manufacture of semiconductor devices, TFTs and the like.
In this regard, various proposals and attempts have been made heretofore to improve the performance of the photoresist compositions. For example, U.S. Pat. No. 3,622,334 discloses that the adhesive bonding strength can be enhanced between a metallic substrate surface and a resist layer formed thereon from a negative-working photoresist composition by the admixture of the photoresist composition with benzimidazole. Japanese Patent Kokai No. 4-46345, on the other hand, discloses a positive-working photoresist composition capable of exhibiting improved adhesion to the surface of a semiconductor silicon substrate by formulating the composition by the admixture of a polymeric resinous ingredient consisting of a polybenzimidazole and having solubility in an organic solvent and a photosensitive diazoquinone compound to a precursor of polybenzoxazole. No successful proposals had been made, however, for the improvement of the adhesive bonding between a substrate surface and a resist layer of a positive-working photoresist composition comprising an alkali-soluble novolac resin as the film-forming agent.
The inventors in Japanese Patent Kokai 6-27657 have previously proposed a positive-working photoresist composition by the admixture of a (poly)benzimidazole compound to a base composition comprising an alkali-soluble novolac resin and a quinonediazido group-containing compound with an object to improve the adhesive bonding between the resist layer and the substrate surface. Although the adhesive bonding can be improved to some extent, however, this photoresist composition has another serious problem that, due to the sublimability of the (poly)benzimidazole compound, sublimation of the additive compound takes place in the course of the post-baking treatment after development to deposit crystalline particles on the inner walls of the treatment chamber which subsequently fall on the work piece in the treatment chamber greatly affecting the subsequent etching treatment of the substrate having the patterned resist layer. Further, Japanese Patent Kokai 2-132442 discloses a positive-working photoresist composition comprising, in addition to an alkali-soluble phenol novolac resin and a photosensitizing agent, an amine compound such as N,N-dialkylaniline compounds by which an improvement can be accomplished for the problem that very fine particles are produced in the resist composition during storage adversely affecting the resolution in the fine patterning of the resist layer.
While it is a current practice in the photolithographic technology using a photoresist composition in consideration of cost saving in the manufacturing process that a volume of the developer solution is used under circulation in a development machine, the developer solution worn out is replaced with a fresh volume of the developer solution less frequently than heretofore. In such a development procedure with prolonged circulation of the developer solution, the effective photo-sensitivity of the photoresist layer is subject to gradual decrease from that with a fresh volume of the developer solution as the developing power of the developer solution is degraded in the lapse of time for the circulation use so that patterning of the resist layer cannot be uniform enough in the accuracy throughout the development work using a volume of the developer solution. This problem due to the circulation use of the developer solution is not limited to the effective photosensitivity of the resist composition alone but the film thickness retention is also affected. Even apart from these problems, photoresist compositions are strongly required to have high stability in the lapse of time after preparation relative to the photosensitivity and film thickness retention.